The paper focuses on certain natural polyphenolic extracts from common elder fruit (Sambucus nigra), and also on their effects in diabetes mellitus. The results reveal that the glycosylated hemoglobin values are much higher in the diabetic group and they are significantly lower in the group protected by polyphenols. The natural polyphenol compounds reduce the lipids peroxides, neutralize the lipid peroxil radicals and inhibit the LDL oxidation. Following the perturbation of the lipid metabolism in the diabetic rats, atherogen risk has significantly increased values in comparison to the rats from the witness groups. It is found that due to the polyphenolic protection of the rats from the diabetic group treated with polyphenols, the atherogen risk is preserved at normal limits. The serum activity of glutathione-peroxidase and superoxide-dismutase has significantly lower values in the diabetic group as compared to the group protected by polyphenols. Through the hypoglycemiant, hypolipemiant and antioxidant effects,Sambucus nigra represents a possible dietary adjunct for the treatment of diabetes and a potential source for the discovery of new orally active agent(s) for future diabetes therapy. Understanding the mechanism through which the natural polyphenols have effects on the functionality of the endothelium cells, including on the membrane sensitivity and intracellular signalling, could represent a new way of therapeutically approaching chronic metabolic diseases and cardiovascular illnesses.